Tern, Tern, Tern -- Pescadero Beach, California (1 Viewer)

For every season, or at least every Summer, we have migrating terns on the California coast. I found a nice group of terns in the lagoon on Pescadero Creek near the ocean beach this morning. Lots of Caspians, and a few not-a-Caspians. I'm pretty sure that I have a couple decent pictures of Elegant Terns, which are a new bird for me. I am a little challenged by sorting out what appear to be a fair number of juvenile Elegants and Caspians in the mix. Here are a few of the better photos, I'd appreciate help from the experts here which ones are which.

My take:
#1 and #2, juvenile Elegant (yellow legs) with adult Caspian
#3 two juvenile Caspians (yellow beaks but black tipped) with an adult Caspian
#4 busy shot, but I think: most are Caspians, especially the clear top bird; the left bird is an adult Elegant (yellow beak, no dark underwing tips, forked tail), along with the blurrier lowest bird
#5 two adult and two juvenile Elegants; the beak on the more central adult looks freakishly long and narrow here

Do I have the hang of Elegant Terns yet?

a couple more

A few more shots of what I think are Elegant Terns. Both the adults and juveniles show the shaggy crest relatively clearly. #3 shows a Caspian for relative size.

It seems like there's a remote chance that Royal Terns could be seen at Pescadero, but I don't think that I see any evidence of that here. But I doubt that I have the skills to tell Royal from Caspian at this point.

The first three photos are all Caspian Terns. In the first photo the front bird is a juv. As you said the size difference is large so when in doubt that's a clear sign. the bird in front here is large and the orange bill/legs is due to immaturity rather than being a different species (notice the scaly back). Notice also the chunky bill shape of Caspian while Elegant has a long thin bill. The fifth photo is all Elegant Terns as are the first two photos of your second posting. The third photo has both species the Caspian being the big bird in the middle. The fourth photograph in your first posting there is Caspian (top) and elegant top left and bottom.

SJC said:

The first three photos are all Caspian Terns. In the first photo the front bird is a juv. As you said the size difference is large so when in doubt that's a clear sign. the bird in front here is large and the orange bill/legs is due to immaturity rather than being a different species (notice the scaly back). Notice also the chunky bill shape of Caspian while Elegant has a long thin bill. The fifth photo is all Elegant Terns as are the first two photos of your second posting. The third photo has both species the Caspian being the big bird in the middle. The fourth photograph in your first posting there is Caspian (top) and elegant top left and bottom.

Click to expand...

Thanks for the input, SJC. Looking at the first two pics again, I see that the birds are the same size, so I should have figured juvenile Caspians for the yellow-billed bird. Where it has wings up (#2), it shows the Caspian black underwing tips, which should have been a clue.

I agree with SJC. Nice size comparison shot in the last photo.

And though Sibley does show juvenile Caspian Terns as having dark legs, leg color should generally be used only as a supporting field mark in my opinion. Among gulls for example, most species show variations in leg color and exceptions to most rules have been found.

Best,
Jim